The Eater of Worlds is one of the five pre-Hardmode bosses. It can only be fought in the Corruption, where it is summoned either by destroying three Shadow Orbs or by using Worm Food (either method is repeatable).

Behavior

The Eater of Worlds uses the same AI as all of the other monsters in the Worms Family. However, unlike other worms, every individual segment has its own health. If you destroy a segment that is neither head nor tail, the Eater of Worlds splits at the spot that was destroyed and each half will continue fighting.

Strategy

Disclaimer: For the purposes of this guide, it is assumed that the player is using a new character in a new world, and would therefore only have access to appropriately-tiered equipment. Otherwise, this boss would be a piece of cake.

General Tips

The head has 65 and 0 defense, the body segments have 150 and 2 defense, and the tail has 220 and 4 defense. In order to function as a monster, each part of the Eater of Worlds needs to have at least two pieces: a head and a tail. If one of the sections of the boss ever has less than that, then the entire section dies. Because of this, destroying every other segment of the boss is the most efficient way to defeat it (though not always the most practical).

Whenever the Eater of Worlds splits, damage to each part remains. Therefore, trying to maximize damage equally across the entire body will generally result in the fastest kill.

Because the head deals so much damage, it is strongly recommended that you avoid it at all costs, even if it means having to move through the boss's body segments (taking damage in the process). Also, it may be a good idea to aim for the head, as not only does it have less defense and HP than a body segment, but splitting the boss up by destroying body segments will only make it more difficult to dodge its attacks. (Focusing on the head should also increase the amount of loot dropped.) When the head is destroyed, the boss will stall for a bit, allowing you to take aim and fire at the new head. If the player is using one of the above recommended weapons, then it is possible for the player to stall the boss this way almost indefinitely, leading to a quick, easy kill.

It is ill advised to fight the Eater of Worlds inside a chasm, as not only can it strike with little warning, but it could also knock you to your death. You could use the Grappling Hook to cling onto a wall, though you should still avoid getting struck by the head as, again, it deals heavy damage to players.

If you don't want to fight the EoW by breaking a shadow orb, but don't have enough Rotten Chunks to make Worm Food you can start building an arena above ground. Just kill any corruption monsters and take the rotten chunks they drop and once you have the arena ready, you should also have enough rotten chunks.

Recommended Items

Since this boss is composed of multiple segments that each have their own HP, weapons that can hit multiple enemies per attack are recommended. These include the Vilethorn, any kind of flail (such as the Ball O' Hurt) and a bow (preferably a Golden Bow or better) with Unholy Arrows, though a Gold Broadsword or better can be used if none of these are available. The Harpoon is also highly useful against this boss, since it's more than capable of striking multiple segments on his body at once if the player stands close enough.

Shuriken: This weapon is ideal for beginner players as it damages lots of the bosses segments which makes it easy to kill.

Crimson Rod:Use this at the start of the battle and then switch and use a weapon above or below.

How-to-get: Smash Pulsuating Hearts

Vilethorn: This weapon does only 8 damage (7 to the body segments), but it's here due to how it can hit multiple enemies several times per attack, so this damage can really add up fast. Moreover, this weapon passes through solid blocks, so it can damage the Eater of Worlds even when it's underground. It uses up 12 mana per use, so you should consider using a different weapon if your max mana is low. The Magic Power Potion will increase the power of this weapon by 20% for 2 minutes.

How-to-get: Smash Shadow Orbs.

Harpoon: Very effective in short range against the Eater of Worlds. It does 25 damage and can fire almost as fast as the Minishark in close range, thus making it a very effective weapon against the Eater of Worlds.

The Eater of Worlds decided to "swim" horizontally along one of the rows of wooden platforms of this arena, which placed it in a good position to get massacred by a player with a bow and Unholy Arrows.

Ball O' Hurt: A neat little trick that you can do with this weapon (as of patch 1.0.6) is that you can toss the ball out, keep it held out by holding down the left mouse button, and it'll damage enemies even when the ball is not moving around. If the Eater of Worlds passes through this, then whatever segments touch this will take continuous damage, which will add up even quicker than what a Vilethorn can dish out.

How-to-get: Smash Shadow Orbs.

Bow with Unholy Arrows: A Gold Bow with Unholy Arrows will do about 19 damage, while a Demon Bow will do about 22 damage. The best time to use this weapon effectively is when the Eater of Worlds is swimming horizontally along the ground (as seen in the picture to the right), allowing you to damage not only the head, but quite a few segments as well. Archery Potions can be used to increase the damage done by 20%.

Silver Armor or better is recommended, as well as having at least 200 . Bring along a few (Lesser) Healing Potions as well, as the head deals a massive 40 damage (minus armor), though the body segments deal only 15 damage by comparison.

The following optional Consumables may also be of some use during this boss battle, if you're willing to use them that is:

Ironskin Potion: Increases your defense by 8 for 5 minutes, allowing you to take 4 points less damage from attacks. Although you should still avoid the head at all costs, it'll at least make the damage inflicted by the body segments less painful.

Thorns Potion: For 2 minutes, enemies that attack you take damage equal to half of the damage that was inflicted upon you. Although this can make the fight go by a bit quicker, you have to take damage for the potion to work. Although many people would rather prefer to not get hurt by the boss's attacks, only using this in case they do get hurt, if you REALLY wanted to use this as a major source of damage, then you're going to have to use up quite a few Healing Potions (and maybe a few Regeneration Potions as well) to keep yourself alive, as the total HP of all of the segments combined is a little over 7000! (7485 total base HP.)

Regeneration Potion: For 2 minutes, your health regeneration is increased. Like the Ironskin Potion, this can also make surviving the Eater of Worlds' attacks a bit easier.

Archery Potion: For 4 minutes, your bow deals 20% extra damage. Works well with a bow loaded with Unholy Arrows.

Magic Power Potion: For 2 minutes, your magic attacks deal 20% extra damage. Works well with the Vilethorn.

Hunter Potion: For 5 minutes, enemies, including the Eater of Worlds, glow. This can make avoiding the Eater of Worlds' attacks easier, as players can even spot it while it's burrowing underground.

Arena

This boss arena was built in the middle of a corrupted area. It was dug underground so that the Eater of Worlds could have some ground to move around in.

Since this boss can only be fought in the Corruption, your arena will need to either be located in the Corruption, or be made out of enough Dirt Blocks covered with corrupted grass and/or Ebonstone Blocks (500 blocks should do the trick) for the game to determine that it lies within a valid corrupted area. The arena doesn't have to be very big (around 75 blocks is a nice width), though it should have a roughly flat surface at the bottom, and at least 2 rows of wooden platforms for avoiding the Eater of Worlds should it decide to swim along the surface of the bottom floor, or one of the rows of wooden platforms. If you'd like, you can dig some holes beneath your arena (and to the sides and above it if it was built underground) to more easily spot the Eater of Worlds before it attacks.

If you built your arena above ground, then you may have to deal with it becoming tangled up more often, as the boss doesn't have much earth to swim around in. However, if you built your arena partially or even fully underground, then the boss shouldn't tangle up as much, and can easily be set up for a quick kill (as mentioned before), though you will have to keep an eye on every side of your screen, as the boss can burst from the walls, or (if deep enough underground) even the ceiling.

Notes

There needs to be at least 500 Ebonstone Blocks nearby in order to be considered inside a valid Corruption area for the purposes of fighting this boss.

From patch 1.0.5 and onwards, the Eater of Worlds would flee after a while if the player wasn't in a corrupt area. Until patch 1.0.6, the player would get the message "Eater of Worlds was defeated.", but now the message says "Eater of Worlds flees."

Trivia

This boss could possibly be a reference to the "Eater Of Worlds" from Stephen King's novel "Night Shift" from the first short story "Jerusalem's Lot".

This boss could be a reference to the 1990 film `Tremors` where giant worms with teeth attack a group of friends.

Bugs

In the iOS version of Terraria, once you break the third shadow orb, the entire Eater of Worlds will spawn in the location of the shadow orb, and the message "Eater of Worlds has awoken!" will not display. "Eater of Worlds has been defeated!" will still display once it has been killed, however.

Rarely, the boss will spawn as only a single segment, and nothing else. It will function the same as normal, just very ineffective at killing anyone.

A possible bug may be that, when building over the Corruption, the boss will be summoned, as if displeased with the bridge, leading to much confusion and claims of griefing.

One very specific bug may happen if the Eater of Worlds is fought in the Underground Jungle. Some of its segments may get "chained/fused" with a Man Eater and stand still.

Another bug is that the boss will be summoned on world creation (i.e. make a world then enter it). This is most likely caused by defeating a boss and then immediately creating the new world.

Sometimes when a Meteorite landed and you exit the world and enter it the boss will be summoned.

Another possible bug is when you've cut the Eater of Worlds into several segments and one kills you, that worm will disappear but the others will continue to fight (needs confirmation).

Sometimes, on console version, on a full server, only one segment will be visible, and only it can be damaged, once destroyed, the next segment will become visible.